Ultra high frequency system



March 24, 1942.

R. w. GEORGE 2,277,638 ULTRA HIGH FREQUENCY SYSTEM Filed June 20, 1939's- Sheits-Sheet 1 20 m6 If i Ll ll 21 30 iii iE-m +raou T 36.3 M 5 L F.ourpuf w (30 MEGS.) .c -+9ou INVENTOR. RALP m GEORGE BY MM ATTORNEY.

March 24, 1942. w, GEORGE 2,277,638

ULTRA HIGH FREQUENCY SYSTEM Filed June 20,1959 3 Sheets-Sheet 2 I EOUTPl/T J 27 INVENTOR.

RALPH W GEORGE BY W A TTORN E Y.

March 24, 1942. w GEORGE 2,277,638

ULTRA HIGH FREQUENCY SYSTEM Filed June 20, 1939 3 Sheets-Sheet 3 V V5mm? PLATES INVEN TOR. RA H W GEORGE BY MM ATTORNEY.

Patented Mar. 24, 1942 ULTRA HIGH FREQUENCY SYSTEM Ralph W. George,Riverhead, N. Y., assignor to Radio Corporation of America, acorporation of Delaware Application June 20, 1939, Serial No. 280,020

26 Claims.

This invention relates to ultra high frequency systems. It isparticularly applicable to receivers suitable for receiving ultra shortwaves of 10 meters and below, and preferably to receivers adapted toreceive ultra high frequency signals anywhere from 30 m'egacycles up tothe order of 600 megacycles. 7

The invention includes novel mechanical and constructional details, andhas for one of its objects to provide a simple and compact frequencyconverter to be used preferably with superheterodyne receivingapparatus, to receive ultra high frequency signals up to frequencies ofthe order of 500 megacycles and 600 megacycles, though not limitedthereto.

Another object of the invention is to provide ultra high frequencydetector and heterodyne oscillator circuits operating at maximumfrequencies limited by the vacuum tube characteristics, and which aretunable by means of variable rotary type condensers.

Still another object is to provide an ultra short wave frequencyconverter of the type referred to above having an ultra high frequencyoscillator circuit wherein means are provided for adjusting theinductance thereof.

A further object is to provide a tuned oscillatory' circuit for ultrahigh frequencies employing a variable condenser in which no leads orconnecting wires are employed between the condenser and the associatedcircuit element of the oscillatory circuit,

A still further object of the present invention is to provide an ultrahigh frequency system utilizing a pair of concentric lines, or anequivalent U-shaped line, having uniformly distributed inductance andcapacitance, with a single vacuum tube oscillator circuit connectedacross the inner conductors of said concentric lines or across the legsof said U.

Another object is to provide an ultra high frequency system utilizingseveral of the foregoing types of frequency converter units in a singlereceiver, any one of which can be selected and its output fed to a'highfrequency amplifier, thus providing a wide range receiver.

A feature of the present invention lies in the use of a concentric linewhose inner conductor constitutes an integral part of a rotary con--denser employed for tuning said concentric line.

Another feature involves the use of a concentric line having an inner'conductor at whose high potential end there is provided a rotarycondenser, the stator plates of which are connected to said innerconductor by extremely low inductance means, thus avoiding the use 'ofleads or connecting wires from the condenser to the concentric line.

A further feature comprises an oscillatory circuit employing a coiledinductance having in series therewith a rotary condenser, certain ofwhose plates are connected tosaid line through extremely low inductancemeans. This inductance is coiled to obtain maximum inductance in assmall a space as possible;

' Other objects,'features and their advantages will appear from areading of the following description, which is accompanied by drawingswherein like parts are represented by like reference numerals throughoutthe figures. In the drawings:

Fig. 1 illustrates diagramatically the equivalent electrical circuit ofan ultra high frequency converter unit embodying the principles of thepresent invention, particularly applicable to a superheterodynereceiver;

Fig. 2 shows an equivalent electrical circuit of the heterodyneoscillator shown in Fig. I;

Fig. 3a shows a front view and Fig. 3b the back view of the essentialelements of a mechanical construction embodying the system of Fig.

Fig. 4 shows the essential elements of a mechanical construction of amodification of the system of Fig. 1 wherein there are employed coiledinductance elements for certain of the oscillatory circuits; Fig. 40 is'a front view of one of the coil inductance elements of Fig. 4 and shows,schematically, the f variable slider 'contacting the coil;

Figs. 5 and 5a respectively show bottom and side views, respectively, ofthe construction of the stator plates of the rotary condensers employedin the present invention: and

Fig.6 shows a side view of a novel type of oscillatory circuit for usein connection with the present invention, wherein one part of the innerconductor constitutes the'stator plates of a rotary condenser. Thisfigure is taken along the lines 66 of Fig. '7, the latter of which showsa plan view of the arrangement of Fig. 6 along the lines l'l but withthe shaft and rotor plates removed.

Referring to Fig. l inmore detail, there is shown a simple compactfrequency converter unit comprising a detector unit '4 to whose gridthere is coupled a tuned input circuit of the concentric inductance typeand to whose cathode is coupled a heterodyne oscillator l3 which iscontrolled as to frequency by'a pair of rodlike inductance elements 9,ID. The tuned input circuit for'detector 4 comprises a concentric linehaving an inner conductor l and an outer grounded conductor l1 directlyconnected to said inner conductor at one end by means of end plate 28.The free or high potential end of inner conductor l is capacitivelycoupled to the adjacent end of the outer conductor I! by means of avariable rotary condenser 2 which will be described in more detaillater. The received signals are collected on an antenna 21, shown hereinby way of example as an unbalanced antenna system which is tapped acrossa portion of the inner conductor l of the tuned input circuit. The tunedinput circuit 1, i1 is tuned to the signal frequency and energytherefrom is passed over tap 26 and lead 3 to the grid of the detectortube 4. At this time it should be noted that the tap 26 as well as thetap from the antenna circuit 21, are adjusted over the inner conductor 2in order to obtain optimum impedance adjustments, the tap to thetransmission line extending to the antenna 21 being adjusted to obtainan impedance match between the tuned input circuit and the antennasystem.

The heterodyne oscillator l3 has its anode connected to the highpotential end of inductance element 9 by means of a by-pass condenser23, which is of low impedance to the oscillator frequency, while thegrid of oscillator 13 is similarly connected to the high potential endof inductance element l by means of a by-pass condenser 22. Thepotential for the anode of the oscillator is supplied through a leadextending through the interior of the inductance element 9 to a sourceof voltage supply whose value as supplied to the anode can be adjustedby means of a tap 20, thereby also controlling the intensity of theexcitation on the cathode of detector 4. The grid of the oscillator II!has connected thereto a grid-leak 29 directly connected across the gridinput condenser 22. This gridleak condenser, if desired, can be locatedexternally of the mechanical construction and connected to the gridthrough a lead extending in the interior of inductance element In,although this last arrangement is not preferred. The cathode of theoscillator is connected to ground through an impedance l4 which reducesthe tendency for parasitic oscillations to occur and improves theefficiency of the oscillator by permitting the cathode to assume themost favorable potentials for maximum intensity of oscillation. Thisimpedance l4 may be a resistor, and in some cases where it is desired toimprove the efilciency of the oscillator it may constitute a smallinductance, the size of which is preferably determined experimentally.In effect. inductance elements 9 and I0 may each be said to constitute aconcentric line tuned circuit, the outer conductor of which is the shellI6 plus an imaginary shield extending symmetrically between and alongthe length of the inductance elements 9 and In. A modification showingsuch a concentric line arrangement is shown in Fig. 6 and describedlater in this specification. The total inductance between the anode andgrid of oscillator Hi can be varied by slider I! which is connectedbetween tubular elements 9 and I0, while the grid inductance l0 can bevaried by slider 2| which is connected between element In and the outergrounded shield. If desired, inductance element 9 can also be variedindependently by another slider in the same manner as inductance I0 isvaried by slider 2!. The frequency of the oscillator is variable bymeans of tuning condenser 12 which comprises two rotary condenserelements bridged in series across the high potential ends of theinductances 9 and Hi. The stator plates of the two rotary condensers ofi2 are directly and integrally connected to the ends of inductanceelements 9 and Ill while the rotor plates are connected to a metallicshaft 32' in the manner indicated in Fig. 3b. Where a vernier adjustmentof the oscillator circuit is desired, there may be provided a Verniertuning condenser I5 which may be operated by suitable automatic controlmeans over a shaft 30 and coupled to drive means, not shown.

The cathode of the detector tube 4 is energized by the heterodyneoscillator l3 via a tap 8 on the inductance element 9 through a couplingcondenser 24 shunted with a self-bias resistor 25. The intermediatefrequency output of the detector is derived from the anode circuit oftube 4 by means of the transformer 5, I, the primary coil 5 of which istuned by the con densers l8 and 6. This intermediate frequency output iscoupled to the intermediate frequency amplifier of the receiver, notshown.

Fig. 2 illustrates the equivalent electrical circuit for the heterodyneoscillator l3. It will be obvious that this circuit is generally of theHartley three-point type, the grid being connected to one end of thetuned frequency controlling circuit, the anode being connected to theother end thereof, while the cathode is coupled to an intermediate pointsuch as the center. Impedance Z, labeled 14, has been shown in box form,since it may constitute a resistance or an inductance whose values canbe most readily determined experimentally. At lower frequencies, theimpedance I4 is usually eliminated. It is not believed necessary to gointo the operation of the circuit of Fig. 2, since it is believed to beapparent from an inspection thereof.

The mechanical construction of apparatus in accordance with Fig. 1 maytake the form indicated in Figs. 3a and 3b, the former of which shows afront view and the latter of which a back view of the sarrie apparatus.Only the essential elements of the circuit of Fig. l have been shown inFigs, 3a and 3b in order to simplify the drawings. It should be notedthat the tuned input circuit includes a square copper shield or outerconductor I! to whose low potential end an antenna 21 is connected. Theantenna 21 is here shown as being a dipole which is connected through abalanced transmission line to both the inner conductor and the outerconductor. This manner of coupling the transmission line to the tunedinput circuit is described in more detail in my application Serial No.292,770, filed August 31, 1939, which has eventuated into United StatesPatent No. 2,234,- 556, granted March 11, 1941. It should be observedthat the condenser 2 is of the multiplate rotary type comprising aplurality of stator plates and a plurality of rotary plates. The statorplates are directly connected to a metallic plate 3| of extremely lowinductance forming part of or integrally mounted on the high potentialend of conductor I, thus obviating the need for leads or conductorsbetween the condenser 2 and the conductor l of the concentric line tunedcircuit. The rotary plates are coupled to a shaft 32' which is groundedto the outer shell l1. It should be understood that the grounding of therotary condenser plates is made with the introduction of no unnecessaryinductance. The constructional details of the method of connecting thestator plates to the inner conductor l are shown in more detail in Figs.5 and 5a. The oscillator I3 is located in a suitable rectangularshielded compartment I5 of its own (note Fig. 3a). The filamlent leadsof this oscillator tube are shown connected to metallic plates 32" whichare mounted on mica sheets to provide by-passing condensers to thepartition wall of the compartment. In like manner, other by-passcondensers used in other parts of the circuit (not shown in Figs. 3a and3b) are similarly constructed to obtain effective by-passing with noseries inductance.

Referring to Fig. 31), it should be observed that the condensers I2 arealso of the rotary type and of similar construction to the condenser 2shown in Fig. 3a. More specifically, there is provided a rotarycondenser for the high potential ends of the lines 9 and II], the statorplates of each rotary condenser being directly mounted on metallicplates 3| which are integral with the conductors 9 and I0, while therotary plates of both condensers l2 are mounted on a single shaft 32'.Reference is made to Figs. 5 and 5a for a more detailed showing of themanner in which the stator plates of these rotary condensers areconnected to the ends of lines 9 and ID. The shaft 32', which connectsthe rotary condenser plates of condenser I2 in series in the mannershown diagrammatically in Fig. 1, may or may not be grounded.

At this time it should be observed that the square shields or tubing forthe conductor I1 and for the box I 6 affords a simple assemblage whichenables the mounting of the various elements on. the walls thereof. Itshould be understood, how ever, that if desired these shields may alsobe cylindrical and have other forms without changing the desiredcharacteristics of the circuit.

Fig. 4 shows an arrangement similar to Fig. 3b except that the straightinductance elements 9 and I have been replaced by small inductancetubular rod-like elements 9' and I0 each of about one and one-halfturns. The size of this coil may, of course, vary with the desiredamount of inductance and may comprise one turn, more or less. Theadditional inductance provided by the coils 9 and I 0' serves to reducethe size of the circuit elements for the lower frequencies to give amore compact structure. It should be noted that if straight linearinductance elements such as 9 and I 0 were employed instead of the coils9' and ID to obtain the same inductance values, the lengths of thelinear elements 9 and I0 would be inconvenient. It is preferred thatcoils 9 and Ill be small copper tubing through the interior of whichleads (labeled 38 and 39) may extend from external sources of supply tothe anode and the grid of the oscillator l3. Rotary condensers 12 (shownin Fig. 4) are similar in construction to the condensers l2 shown inFig. 317. It should be observed that, except for the use of coils 9' andIII, the arrangement of Fig. 4 is very similar to the arrangement ofFigs. 3a and 3b.

Figs. 6 and '7 show a modification in construction of the heterodyneoscillator circuit l3 of the invention. In these figures the inductanceelements 9" and I0" each constitute the inner conductors of a concentricline oscillatory circuit. The outer conductor of each concentric lineoscillatory circuit of these figures constitutes the inner surface of acylindrical hole formed from a solid block of metal 31, although itshould be understood that, if desired, the outer conductor may alsocomprise a thin shell of material. The inner conductors 9" and I0 of theconcentric line oscillatory circuits are each machined at their highpotential ends to provide suitable stator plates integral with the innerconductors for the rotary condensers l2". In effect, each of the innerconductors 9" and I0" have a pair of flanges 34 at the free end thereofwhich are spaced from each other by a slot or groove cut into the innerconductor. These flanges form stator plates between which the rotaryplate 35 of the condenser l2 moves. The rotary plates 35, 35 of bothcondensers are electrically connected together and controlled in unisonby metallic condenser shaft 32'. In order to tune each concentric lineincluding the inner conductors 9" and I0", there is provided a smallpadding condenser constituted by a movable metallic plate 36 which isadjustable in position over the free ends of the inner conductorsadjacent the stator plates 34. This arrangement is clearly shown in Fig.'7, wherein the arrows indicate the direction of movement of the plates36 between the inner and outer conductors of each concentric lineoscillatory circuit. The ends of plates 36 which are immediately abovethe conductors 9 and ID" are separated therefrom by a suitabledielectric which may be air or some insulating material. The oscillator[3 may be mounted between the conductors 9" and I0 so that the anode andgrid electrodes contact small metal plates 23' and 22' which formcapacitors with those surfaces of the inner conductors 9" and ID"adjacent the flanges 34, thus providing anode and grid couplingcondensers equivalent to condensers 23 and 22, respectively, of Fig. 1.Putting it another way, the grid and anode of oscillator 13 of Figs. 6and 7 are coupled to the elements 9" and H1" in the same manner as theoscillator I3 is coupled to the inductance elements 9 and ll) of Fig. 1.The arrangement shown in Figs. 6 and 7 has the advantage of givingextremely high frequency stability at the high frequency range around500 megacycles for circuits employing lumped circuit elements for tuningthe line.

It is proposed to employ several circuits of the type shown in thedrawings to cover different ranges of signal frequencies. For example,one such circuit may cover a signal range greater than 250 to 500megacycles while another such circuit may cover a signal range greaterthan 125 to 250 megacycles, while still a third circuit may cover asignal range greater than to megacycles. In this way the different unitswill overlap in frequency range to provide continuous frequency coveragecapabilities. These three frequency converters may then be mounted sideby side on a panel, any one of which can be connected with a commonintermediate frequency amplifier by suitable switches, although, ifdesired, they could also be of the plug-in type. In this manner, thereis obtained a simplified, extremely wide range, and compact ultra highfrequency receiver.

What is claimed is:

1. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of rod-likeinductance elements arranged parallel to each other and electricallyconnected to each other at one end and having a balanced tuningcondenser arrangement coupling together the other ends of saidinductance elements, a shield surrounding said inductance elements, aconnection from said cathode to said shield, and paths of low impedanceto energy of the operating frequency from said last ends of saidinductance elements to said anode .and control electrode.

2. An oscillation generator in accordance with claim 1, characterized inthis that said inductance elements are tubular, there being a leadextending within one of said tubular elements for supplying a polarizingpotential to said anode.

3. An oscillation generator in accordance with claim 1, characterized inthis that said inductance elements are tubular, there being leadsextending within said elements for providing suitable bias potentials tosaid anode and grid.

4. An oscillation generator in accordance with claim 1, characterized inthis that said inductance elements are coiled and tubular, there beingleads extending within said elements for providing suitable biaspotentials to said anode and grid.

5. The combination with an oscillation generator comprising an electrondischarge device having an anode, a cathode, and a control elec trode; apair of rodlike inductance elements arranged parallel to each other andelectrically connected to each other at one end, and having a balancedtuning condenser arran einent coupling together the other ends of saidinductance elements, a shield surrounding said inductance elements, aconnection from said cathode to shield, paths of low impedance to energyof the operating frequency from said last ends of said inductanceelements to said anode and control electrode, of a vacuum tubeutilization circuit coupled to one of said inductance elements.

6. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode; a tuned circuitincluding a pair of straight tubular inductance elements ofsubstantially the same diameter arranged parallel to each other anddirectly connected together at one end, and having a balanced condenserarrangement coupling together the other ends of said inductanceelements, paths of low impedance to energy of the operating frequencyfrom said last ends of said inductance elements to said anode and saidcontrol electrode, a connection from said cathode to the electricalcenter of said balanced condenser arrangement, and a slider for varyingthe effective lengths of said inductance elements with a consequent variation of the total inductance between the an ode and control electrode.

7. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit including a pair ofspaced tubular inductance elements arranged parallel to each other anddirectly connected together at one end and capacitively coupled togetherat their other ends, paths of 10W impedance to energy of the operatingfrequency from said last ends of said inductance elements to said pairof cold electrodes, means for varying the total inductance of said pairof elements, and separate means for varying the inductance of one ofsaid inductance elements.

8. A high frequency signalling system including an oscillation generatorcomprising an elec tron discharge device having a pair of coldelectrodes, a tuned circuit including a pair of substantially identical,spaced, tubular inductance elements arranged parallel to each other anddirectly connected together at one end and capacitively coupled togetherat their other ends, paths of low impedance to energy of the operatingfrequency from said last ends of said inductance elements to said pairof cold electrodes, and vacuum tube utilization apparatus coupled to apoint on one of said inductance elements intermediate its ends.

9. A high frequency signalling system including a vacuum tube oscillatorhaving an anode and a grid, a tuned circuit comprising a pair ofsubstantially identical inductance elements arranged parallel to eachother and directly connected together at one end and capacitivelycoupled together at their other ends, capacitive paths of low impedanceto energy of the operating frequency from said last ends to said anodeand grid, and vacuum tube utilization apparatus coupled to a point onthat inductance element which is capacitively coupled to said anode.

10. An ultra high frequency receiver comprising a high frequencydetector having a grid, anode and cathode, a tuned input circuit coupledto said grid, an antenna coupled to said tuned circuit, an oscillatorcoupled to said cathode, and an intermediate frequency amplifier coupledto said anode, said oscillator including a vacuum tube having an anode,a cathode and a grid, a tuned circuit comprising a pair of rod-likeinductance elements arranged parallel to each other and directlyconnected together at one end and capacitively coupled together at theirother ends, capacitive paths of low impedance to en ergy of theoperating frequency from said last ends to the anode and grid of saidoscillator, and means for coupling said cathode of said oscillator to apoint effectively intermediate said last ends of said inductanceelements.

11. A receiver in accordance With claim 10, characterized in this thatsaid first tuned circuit is a concentric line and the cathode of thedetector is coupled to a point on the anode inductance element of saidoscillator.

12. An oscillation generator comprising an electron discharge devicehaving an anode and a grid, a tuned circuit coupled between said anodeand grid and comprising a pair of tuned concentric lines whose innerconductors form linear inductance elements, said linear inductanceelements being directly connected together at one end and capacitivelycoupled together at their other ends, and paths of low impedance toenergy of the operating frequency from said last ends of said inductanceelements to said anode and grid.

13. An oscillation generator comprising an electron discharge devicehaving an anode and a grid, a tuned circuit coupled between said anodeand grid and comprising a pair of tuned concentric lines whose innerconductors form inductance elements, said inductance elements beingdirectly connected together at one end and capacitively coupled togetherat their other ends, paths of low impedance to energy of the operatingfrequency from said last ends of said inductance elements to said anodeand grid, and means for individually tuning each of said concentriclines.

14. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit arrangement includinga pair of spaced rod-like inductor elements arranged substantiallyparallel to each other and coupled together at one end by a path of lowimpedance to energy of the operating frequency, capacitive paths of lowimpedance to energy of the operating frequency from the other ends ofsaid inductor elements to said pair of cold electrodes, shielding meanssurrounding said inductor elements, and means for varying the effectiveinductance of said rod like elements.

15. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit arrangement includinga pair of spaced rod- "he inductor elements arranged substantiallyparallel to each other and directly connected together at one end, theother ends of said rod-like inductor elements being capacitively coupledtogether, and capacitive connections of low impedance to energy of theoperating frequency extending from said last ends to said pair of coldelectrodes, shielding means surrounding said inductor elements, andmeans for varying the effective inductance of said inductor elements.

16. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit comprising a pair ofinductance elements which are similar in shape and size, each elementhaving a low potential end and a high potential end, a connection of lowimpedance to energy of the operating frequency between the low potentialends of said elements, and capacitive connections of low impedance toenergy of the operating frequency from the high potential ends of saidelements to said pair of cold electrodes.

17. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a grid, a tuned circuit comprising a pairof inductance elements which are similar in shape and size, each elementhaving a low potential end and a high potential end, a connection of lowimpedance to energy of the operating frequency between the low potentialends of said elements, means eiiectively coupling said connection tosaid cathode, and connections of low impedance to energy of theoperating frequency from the high potential ends of said elements tosaid anode and cathode.

18. An oscillation generator in accordance with claim 8, includingshielding means for said inductance elements and a connection from saidshielding means to ground.

19. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit comprising a pair ofinductance elements which are similar in shape and size, each elementhaving a low potential end and a high potential end, a connection of lowimpedance to energy of the operating frequency between the low potentialends of said elements, a condenser arrangement having rotor and statorplates and coupling the said high potential ends of said elementstogether, and capacitive connections of low impedance to energy of theoperating frequency from the high potential ends of said elements tosaid pair of cold electrodes.

20. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of rod-likeinductance elements arranged in parallel planes and electricallyconnected to each other at one end and having a tuning condenserarrangement coupling together the other ends of said inductanceelements, a shield surrounding said'inductance elements, a connectionfrom said cathode to said shield, and electrically conductingconnections from said last ends of said inductance elements to saidanode and control electrode.

21. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of noncoaxialhollow tubular inductance elements arranged parallel to each other, aconnection between one end of one inductance element and the adjacentend of the other inductance element, means effectively connecting saidcathode to said connection, a condenser coupling together the other endsof said inductance elements, leads extending within said tubularelements for providing suitable bias for said anode and controlelectrode, and capacitive connections from the other ends of saidinductance elements to said anode and control electrode.

22. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of noncoaxialhollow tubular inductance elements arranged parallel to each other, aconnection between one end of one inductance element and the adjacentend of the other inductance element, means elTectively connecting saidcathode to said connection, a condenser coupling together the other endsof said inductance elements, leads extending within said tubularelements for providing suitable bias for said anode and controlelectrode, capacitive connections from the other ends of said inductanceelements to said anode and control electrode, and an output circuitcoupled solely to one of said tubular inductance elements at a pointintermediate the ends thereof.

23. An oscillation generator comprising an electron discharge devicehaving a pair of cold electrodes, a tuned circuit arrangement includinga pair of spaced rod-like inductor elements arranged in parallel planesand coupled together at one end by a path of low impedance to energy ofthe operating frequency, capacitive paths of low impedance to energy ofthe operating frequency from the other ends of said inductor elements tosaid pair of cold electrodes, and means engaging both inductor elementsfor varying the total inductance between said pair of cold electrodes.

24. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of rodlikeinductance elements arranged parallel to each other and electricallyconnected to each other at one end and having a tuning condenserarrangement coupling together the other ends of said inductanceelements, a shield surrounding said inductance elements, a connectionfrom said cathode to said shield, and connections from said last ends ofsaid inductance elements to said anode and control electrode.

25. An oscillation generator comprising an electron discharge devicehaving an anode, a cathode and a control electrode, a pair of rodlikeinductance elements arranged parallel to each other and electricallyconnected to each other at one end and having a capacity frequencydetermining element coupled to the other ends of said indutcanceelements, a shield surrounding said inductance elements, a connectionfrom said cathode to said shield, and connections from said last ends ofsaid inductance elements to said anode and control electrode.

26. A high frequency signalling system including an oscillationgenerator comprising an electron discharge device having a pair of coldelectrodes, a tuned circuit including a pair of similar inductanceelements arranged parallel to each other and electrically connected toeach other at one end and capactively coupled together at their otherends, shielding means surrounding said inductance elements, paths of lowimpedance to energy of the operating frequency from said last ends ofsaid inductance elements to said pair of cold electrodes, and vacuumtube utilization apparatus coupled to one of said inductance elements.

RALPH W. GEORGE.

